The present invention relates to a machine for automatically assembling uppers of shoes, slippers, boots and the like directly on assembly forms or lasts.
As is known, presently an upper is formed or shaped so as to say, according to substantially two main procedures, before applying the sole.
According to a first method traditionally used, the leather or whatever material the upper consists of, is formed and modelled in appropriate assembly machines of known type and well known to experts skilled in the art. In this traditional assembly, a series of successive operations are carried out according to each of which only one part of the upper is formed. Once the upper has been completely assembled, it is removed and attached, e.g. by means of gluing, to a sole, or inserted in a mould for direct moulding with the sole, e.g. by means of injection or vulcanizing machines.
According to another method, commonly known as American string assembly, also known as Ficelle, or string lasting, the material constituting the upper, already cut and sewed but not yet assembled, is fitted on the metallic form of a mould and with the aid of a string slidingly withheld along the margins of the upper, it is bent along its edges so as to obtain the desired form of the upper. In more detail, with this method, a string, held in place by an appropriate stitch and arranged so as to cross over itself in the front section of the upper, is inserted in loops provided along the edges of the upper which has not yet been formed. The ends of the string are made to project close to the shank so that if it is pulled, it tightens the leather or whatever and causes it to adhere to the metallic form of the mould.
Since the string intersects in a certain section, it blocks itself and it is therefore possible to cut the projecting strings without releasing it.
With this method however, the shanks which have to adhere onto the portion of the mould with the narrowest section, remain raised and it is necessary to fix them in adhering position by manually hooking them onto suitable pegs projecting from the narrowest section of the mould.
It has just recently been realized what great advantages, in terms of production rate and reduction of costs, can be obtained by direct formation of an upper on an assembly form, even directly insertable into a mould having the function of male element, for attachment to the sole. For this purpose, string assembly, Ficelle or string lasting is particularly useful, but a serious inconvenience has to be overcome: it is not possible to make a form of common type with fixed pegs or the like for hooking the shank portions of the uppers, without substantially modifying its structure and function. An attempt to solve the problem has been made, by means of an artifice which consists in fixing onto the insole, engaged on the assembly form, an insert made of steel or resin having these pegs or like members projecting towards the sole on which to hook the shanks. The insert will remain embedded in the sole during its formation. In this manner however, the use of an additional element is indispensable. The actual insert, appropriately made and shaped, is expensive and requires for its application an additional operation which slows down the production cycle of the shoe. Furthermore it should be mentioned that all the fitting operations of the uppers to the form are substantially manual in that they depend on the action and capability of skilled labour and therefore particularly costly, even when the use of instruments such as for pulling of the strings, are reverted to for facilitating the work.